While it’s common knowledge that maternal age affects success rates for intrauterine insemination, data released at the 2014 Annual Meeting of American Urological Association shows that paternal age has a big impact too.

Data from 18.806 intrauterine inseminations over 8 years was studied to assess the impact of paternal age on success rates, with success defined as live birth. The study is the largest to date to track outcomes from this fertility treatment.

The results showed that, after adjusting for general predictors of success (maternal age, maternal BMI, hormone levels and antral follicle counts), there was a clear decline in success rates with advancing paternal age. The decline began when men were in their 20s and continued at 20% for each advancing decade.

In addition to standard success rates, increased paternal age was associated with a variety of other disorders including autism and ADD. Dr. Bar-Chama, part of the team conducting the study, stated that “Historically, we have looked at female age as a limiting factor in fertility, and our take-home message is that paternal age is also a contributor.”

Dr Bar-Chama has called for further research to define the causes of the decline and possible risk factors that contribute to it; “if we can identify modifiable risk factors, we may provide therapies that will be able to counterbalance this observed effect of paternal aging on fertility.”